#include <key.h >

unsigned char key_read()
{
unsigned char temp = 0;
P44 = 0; P42 = 1; P35 = 1; P34 = 1;
if(P33 == 0)	temp = 4;
if(P32 == 0)	temp = 5;	
if(P31 == 0)	temp = 6;	
if(P30 == 0)	temp = 7;	

P44 = 1; P42 = 0; P35 = 1; P34 = 1;
if(P33 == 0)	temp = 8;
if(P32 == 0)	temp = 9;	
if(P31 == 0)	temp = 10;	
if(P30 == 0)	temp = 11;	

P44 = 1; P42 = 1; P35 = 0; P34 = 1;
if(P33 == 0)	temp = 12;
if(P32 == 0)	temp = 13;	
if(P31 == 0)	temp = 14;	
if(P30 == 0)	temp = 15;	

P44 = 1; P42 = 1; P35 = 1; P34 = 0;
if(P33 == 0)	temp = 16;
if(P32 == 0)	temp = 17;	
if(P31 == 0)	temp = 18;	
if(P30 == 0)	temp = 19;	

return temp;
}	